Making widgets partly overlap in a Qt layout

Question

I am trying to make widgets overlap partly in a Qt layout. My current layout is the following, achieved with a QVBoxLayout containing four QHBoxLayout children:

I'm trying to regroup cards of the same suit, in order to achieve something like this (note that there is horizontal and vertical overlapping):

Unfortunately, all the Qt documentation and all the Stack Overflow posts I have read try to avoid widgets overlapping rather than to seek it. Maybe there's a way to set negative spacing between widgets, or forcing a layout to have a maximum width calculated (e.g. according to the number of cards of one suit in this case)? Or do I have to create a custom layout? Maybe I should not be using layouts at all?

If it's any help, I'm adding the widgets to the layouts with code that looks like this:

hLayout[card.getSuit()-1]->addWidget(cardWidget, 0, align);

Answer 1

You will need to implement a subclass of QLayout. There is a detailed example in the QT documentation addressing exactly you problem: Layout Management

Basically, you will need to define the following:

• A data structure to store the items handled by the layout. Each item is a QLayoutItem.

• addItem(), how to add items to the layout.

• setGeometry(), how to perform the layout.

• sizeHint(), the preferred size of the layout.

• itemAt(), how to iterate over the layout.

• takeAt(), how to remove items from the layout.

In most cases, you will also implement minimumSize().

Below I have copied the most important part of the code in the example, for your convenience:

class CardLayout : public QLayout
{
public:
    CardLayout(QWidget *parent, int dist): QLayout(parent, 0, dist) {}
    CardLayout(QLayout *parent, int dist): QLayout(parent, dist) {}
    CardLayout(int dist): QLayout(dist) {}
    ~CardLayout();

    void addItem(QLayoutItem *item);
    QSize sizeHint() const;
    QSize minimumSize() const;
    int count() const;
    QLayoutItem *itemAt(int) const;
    QLayoutItem *takeAt(int);
    void setGeometry(const QRect &rect);

private:
    QList<QLayoutItem*> list;
};


void CardLayout::setGeometry(const QRect &r)
{
    QLayout::setGeometry(r);

    if (list.size() == 0)
        return;

    int w = r.width() - (list.count() - 1) * spacing();
    int h = r.height() - (list.count() - 1) * spacing();
    int i = 0;
    while (i < list.size()) {
        QLayoutItem *o = list.at(i);
        QRect geom(r.x() + i * spacing(), r.y() + i * spacing(), w, h);
        o->setGeometry(geom);
        ++i;
    }
}